Apart from PTFE, very few polymers command the respect of PVDF when it comes to chemical applications. However, Polyvinylidene fluoride, commonly known as PVDF, is a high-performance polymer with a remarkable combination of properties that make it invaluable in numerous different industries. This versatile material possesses unique characteristics, including excellent chemical resistance, high thermal stability, piezoelectric properties, and remarkable electrical insulation capabilities.
While we at Poly Fluoro have always worked with PVDF by machining parts from extruded rods, we were recently presented with the opportunity to develop compression moulded and injection moulded parts using this amazing polymer. The results were more than satisfactory and put us in an exclusive league of companies that can make both large, machined components using compression moulding, as well as smaller intricate parts using our specially developed, high-temperature injection moulding press.
Before we delve any deeper into processing, let us look at some of the properties and applications of PVDF.
Properties of PVDF
1. Chemical Resistance
PVDF exhibits exceptional resistance to a wide range of chemicals, including acids, bases, and solvents. This property makes it ideal for use in corrosive environments, such as chemical processing plants and laboratories. It can withstand exposure to harsh chemicals without degrading or losing its integrity, ensuring long-term reliability.
2. High Thermal Stability
PVDF can operate at elevated temperatures without losing its mechanical properties. It has a high melting point, typically around 177°C (350°F), making it suitable for applications that involve exposure to heat. This thermal stability is particularly important in industries like aerospace, where materials must endure extreme conditions.
One of PVDF's most intriguing properties is its piezoelectricity. When subjected to mechanical stress or pressure, PVDF generates an electrical charge. This property is crucial in various applications, such as sensors, transducers, and actuators, where the conversion of mechanical energy into electrical signals is necessary.
4. Excellent Electrical Insulation
PVDF is an outstanding electrical insulator, making it essential in the electronics industry. Its high dielectric strength and low dielectric constant allow it to insulate and protect electronic components from electrical interference and damage. This property is invaluable in the manufacturing of cables, capacitors, and electrical connectors.
5. UV Resistance
PVDF is highly resistant to ultraviolet (UV) radiation, which can degrade many other materials over time. Its UV resistance makes it suitable for outdoor applications, such as solar panels, architectural cladding, and signage, where prolonged exposure to sunlight is inevitable.
6. Low Density
PVDF has a relatively low density compared to many other engineering plastics. It has a specific gravity of 1.8 compared to PTFE, which is at 2.25. This characteristic makes it lightweight, which is advantageous in industries like aerospace and automotive, where weight reduction is a critical factor in enhancing fuel efficiency and overall performance.
Applications of PVDF
In the aerospace industry, PVDF is used in a wide range of applications due to its exceptional properties. It is employed in aircraft components such as fuel lines, insulation for wiring, and lightweight structural parts. Its resistance to extreme temperatures and chemicals makes it suitable for aircraft exposed to harsh environments.
PVDF's excellent electrical insulation properties make it a key material in the electronics sector. It is utilized in the manufacturing of cables, wire coatings, and printed circuit boards. Its piezoelectricity also finds application in sensors and transducers for detecting and measuring physical parameters.
3. Chemical Processing
PVDF's chemical resistance makes it a top choice for the chemical processing industry. It is used in the construction of pipes, valves, pumps, and storage tanks that transport and store corrosive chemicals safely. PVDF-lined equipment ensures the integrity of chemical processes and prevents contamination.
4. Renewable Energy
The solar energy sector benefits from PVDF's UV resistance. It is used as a protective material in solar panels, where it helps extend their lifespan and maintain their efficiency by shielding them from the harmful effects of UV radiation. PVDF's lightweight nature is also an advantage in solar panel design.
5. Medical Devices
In the medical field, PVDF is employed in various applications due to its biocompatibility and resistance to sterilization methods. It is used in medical tubing, catheters, and surgical instruments. Its piezoelectric properties are harnessed in ultrasound transducers for medical imaging.
6. Architectural Cladding
PVDF is a popular choice for architectural cladding materials in construction. It is used in the form of coatings on aluminium, steel, or other substrates to provide durable and aesthetically pleasing facades for buildings. Its UV resistance ensures that the cladding retains its colour and appearance over time.
7. Oil and Gas Industry
In the oil and gas sector, PVDF is used in applications that require resistance to harsh chemicals and high temperatures. It is utilized in the production of seals, gaskets, and liners for equipment used in drilling, refining, and transporting petroleum products.
8. Water Treatment
PVDF membranes are employed in water treatment processes, such as ultrafiltration and microfiltration. These membranes effectively remove contaminants and microorganisms from water sources, ensuring the production of clean and safe drinking water.
PVDF's lightweight properties make it valuable in the automotive industry for reducing vehicle weight, thereby improving fuel efficiency and reducing emissions. It is used in components like fuel lines, engine components, and interior trim parts. The recent spike in electric vehicle manufacturing had put tremendous pressure on PDFV, as it happens to be ideal for use in a variety of areas essential to EV manufacturing.
PVDF can be extruded, compression moulded, or injection moulded. While it does require a higher temperature as compared with nylons, POM, or ethylenes, the temperature is still well below what it might take to process PEEK, PTFE, or PI (Vepel). Nonetheless, like all high-performance polymers, care needs to be taken on the selection of metals used in the moulding process, as these can very easily corrode when the polymer reaches its liquid state.
In its liquid state, PVDF is viscous enough that it tends not to leak out from a well-designed mould or die. At the same time, the viscosity is not so high that there are issues with cracks or blowholes. Provided enough pressure is given during the moulding (either compression or injection), the voids are easily removed, and the polymer generally behaves well. Unlike PEEK, which only melts at temperatures above 400°C and gives of effluents that need to be removed at high pressures of over 400Bar, PVDF melts at a far more sedate 200-250°C and at pressures of only 100Bar. Further, PVDF also has the option of being melted in a separate die and allows itself to be transferred to another die, where the pressure is applied to give it form. This makes it easier to process than PEEK, where it can sometimes take upwards of 4 hours to even mould a single piece.
Recent spikes in demand for PVDF (driven mainly by the EV boom globally), had pushed the price of raw materials up to the point where industrial applications were being priced out of the market. However, capacity expansions around the world have now brought the prices to more stable levels and the industry is once again looking poised for amazing things.
PVDF's unique combination of properties, including chemical resistance, high thermal stability, piezoelectricity, and excellent electrical insulation, means that it finds application in all corners of industry. From aerospace and electronics to renewable energy and medical devices, PVDF plays a pivotal role in enhancing the performance, durability, and reliability of numerous products and applications. As technology continues to advance, the versatility of PVDF will likely lead to even more innovative uses in the future, making it a material of enduring importance in the world of materials science and engineering.